The present invention relates to a technique of data duplication control in a computer system.
It is a matter of course that as for a public or corporate infrastructure system, being responsible for social infrastructure, a high availability is pursued. In particular, nowadays, it is necessary to devise a countermeasure as to recovery works (disaster recovery) of the system after the event of disaster. In this regard, data stored in a main data center (site) is copied in a storage device at a sub data center as data backup. With this configuration, it is possible to continue operations even in disaster situations, by use of the data copied in the storage at the sub data center.
For example, Japanese Patent Laid-open Publication No. 2001-318833 (hereinafter, referred to as “Patent Document 1”) discloses a storage subsystem having a volume copying function to copy data by volume. Here, the “volume” indicates a logical unit to manage a storage medium (for example, a magnetic disk and the like) for storing data.
In Japanese Patent Laid-open Publication No. 2003-122509 (hereinafter, referred to as “Patent Document 2”) there is disclosed a disaster recovery system which performs data transfer among three data centers. This disaster discovery system holds data in each of the three data centers, thereby reducing data loss, as well as it maintains a configuration being prepared for disaster recovery, even after one data center is lost in the event of a disaster. Here, the “data loss” indicates that if a transfer delay occurs due to a long distance between the data centers and a disaster occurs during the delay time, data that is to be transferred during that time will be lost.